Most conventional lighting fixtures, such as the pendant and the ceiling lighting fixture shown in FIGS. 5 and 6, respectively, have a main body made of a metal material, such as aluminum alloy, aluminum, copper, iron, steel, etc. It is known that metals have relatively high density. When the metal main bodies of the conventional lighting fixtures have an increased wall thickness, the lighting fixtures would have a largely increased overall weight.
Meanwhile, to enable a stable use of the lighting fixture, most lighting fixtures would have a ballast mounted therein. The ballast internally includes a heavy transformer, which endangers the wall strength of the lighting fixture main body. To ensure a sufficient pressure strength, the conventional lighting fixture main bodies made of aluminum alloy, extruded aluminum, or even die-cast aluminum usually have a wall thickness more than 2 mm, resulting in increased overall volume and weight of the completed lighting fixtures and preventing the lighting fixtures from convenient use thereof. As to other types of metal materials, they are difficult to machine or process, and therefore require high manufacturing cost.
While a plastic material may be used to overcome the difficulties in forming the lighting fixture main bodies with metal materials, the plastic material has poor heat resistance and heat radiating ability to cause problems in the safety use of the heat-producing lighting fixtures. That is why most lighting fixtures, particularly the high bay and the ceiling lighting fixtures, do not use plastic materials to form the main bodies thereof.
As a result, most currently commercially available lighting fixtures, particularly high bay and ceiling lighting fixtures, are bulky, uneasy to assemble, and expensive due to high manufacturing cost thereof. Moreover, the biggest problem with the main bodies of the conventional lighting fixtures is they do not include any reinforcing structure to provide sufficient pressure strength.
It is therefore tried by the inventor to develop an improved lighting fixture structure to overcome the problems existed in the conventional lighting fixtures.